1. Field of the Invention
The present invention relates to a process of grinding the back of a wafer in the manufacturing of a semiconductor device. More particularly, the present invention relates to grinding apparatus for grinding the back of a semiconductor wafer and to a method of fixing a grinding plate in an assembly of the grinding apparatus.
2. Description of the Related Art
A semiconductor wafer is subjected to a back grinding process after a device is formed on the semiconductor wafer and before the device is packaged. The back grinding process includes attaching a tape to and over the front of the wafer, subsequently grinding the back of the wafer, and then removing the tape from the front of the wafer. This so-called back grinding process is performed to reduce the thickness of the wafer enough so that the resulting structure can be assembled in a package.
The apparatus for carrying out the back grinding process includes a support for stably supporting a semiconductor wafer, and a grinding assembly disposed above the support and capable of grinding the back side of the semiconductor wafer. The grinding assembly includes a grinding mount, a grinding plate attached to a lower portion of the grinding mount for grinding the back side of the semiconductor wafer, and a driving motor connected to the grinding mount via a rotary shaft for rotating the grinding plate.
FIG. 1A and FIG. 1B illustrate a conventional grinding assembly 30 of semiconductor wafer back-grinding apparatus. Referring to these figures, a grinding mount 20 is provided with a plurality of bolt holes 24 into which bolts 22 are inserted. A grinding plate 10 has threaded holes 12 in the top thereof at locations corresponding to the locations of the bolt holes 24. The bolts 22 extend through the bolt holes 24 and are threaded to the grinding plate 10 within the corresponding threaded holes 12, respectively. A driving motor (not shown) is connected to the grinding mount 20 by a rotary shaft 26 to rotate the grinding plate 10. Reference numeral 14 designates grinding projections which grind the back side of the semiconductor wafer.
In order to attach the grinding plate 10 to the grinding mount 20, the grinding plate 10 must first be aligned with the bottom of the grinding mount 20. Then the grinding plate 10 is fastened to the grinding mount 20 with the bolts 22. In this case, however, the forces exerted by the bolts 22 on the grinding plate may differ, thereby making it difficult to properly level the grinding plate 10, i.e., thereby making it difficult to ensure that the tips of the grinding projections 14 all lie in a horizontal plane. That is, it is time-consuming to accurately position the grinding plate 10 relative to a wafer when fastening the grinding plate 10 to the grinding mount 20.